import sys
import pygame
from ship import Ship
from bullet import Bullet
from alien import Alien
from time import sleep

def check_keydown_events(event,ai_settings,screen,ship,bullets):
    """响应按键"""
    #print('anxia' + str(event.key))
    if event.key == pygame.K_RIGHT:
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        ship.moving_left = True
    elif event.key == pygame.K_SPACE:
        # 创建新子弹并将其加入到编组bullets中
        fire_bullet(ai_settings, screen, ship, bullets)
    elif event.key == pygame.K_q:
        sys.exit()

def fire_bullet(ai_settings, screen, ship, bullets):
    """如果还没有到达限制， 就发射一颗子弹"""
    #创建新子弹， 并将其加入到编组bullets中
    #print('第  '+str(len(bullets))+'  颗子弹')
    if len(bullets) < ai_settings.bullets_allowed:
        new_bullet = Bullet(ai_settings , screen, ship)
        bullets.add(new_bullet)


def check_keyup_events(event,ship):
    """响应松开"""
    #print('songkai'+str(event.key))
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False

def check_events(ai_settings,screen,ship,bullets):
    """响应按键和鼠标事件"""
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()

        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event,ai_settings,screen,ship,bullets)

        elif event.type == pygame.KEYUP:
            check_keyup_events(event,ship)

        elif event.type == pygame.K_SPACE:
            check_keydown_events(event, ai_settings, screen, ship, bullets)


def update_bullets(ai_settings, screen, ship, aliens, bullets):
    """更新子弹的位置， 并删除已消失的子弹"""
    # 更新子弹的位置
    bullets.update()
    # 删除已消失的子弹
    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)

    check_bullet_alien_collisions(ai_settings, screen, ship, aliens, bullets)

def check_bullet_alien_collisions(ai_settings, screen, ship, aliens, bullets):
    # 检查是否有子弹击中了外星人
    # 如果是这样， 就删除相应的子弹和外星人
    collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)
    if len(aliens) == 0:
        # 删除现有的子弹并新建一群外星人
        bullets.empty()
        create_fleet(ai_settings, screen, aliens, ship)




def update_screen(ai_settings, screen, ship, aliens, bullets):
    """更新屏幕上的图像， 并切换到新屏幕"""

    # 每次循环时都重绘屏幕
    screen.fill(ai_settings.bg_color)

    # 在飞船和外星人后面重绘所有子弹
    for bullet in bullets.sprites():
        bullet.draw_bullet()

    ship.blitme()
    #alien.blitme()
    aliens.draw(screen)

    # 让最近绘制的屏幕可见
    pygame.display.flip()



def get_number_aliens_x(ai_settings, alien_width):
    """计算每行可容纳多少个外星人"""
    available_space_x = ai_settings.screen_width - 2 * alien_width
    number_aliens_x = int(available_space_x / (2 * alien_width))
    return number_aliens_x


def get_number_rows(ai_settings, ship_height, alien_height):
    """计算屏幕可容纳多少行外星人"""
    available_space_y = (ai_settings.screen_height -
                        (3 * alien_height) - ship_height)
    number_rows = int(available_space_y / (3 * alien_height))
    print('available_space_y='+str(available_space_y)+'   number_rows='+str(number_rows))
    return number_rows


def create_alien(ai_settings, screen, aliens, alien_number, row_number):
    """创建一个外星人并将其放在当前行"""
    alien = Alien(ai_settings, screen)
    alien_width = alien.rect.width
    alien.x = alien_width + 2 * alien_width * alien_number
    alien.rect.x = alien.x
    alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
    aliens.add(alien)


def create_fleet(ai_settings, screen, aliens,ship):
    """创建外星人群"""

    # 创建一个外星人， 并计算一行可容纳多少个外星人
    # 外星人间距为外星人宽度
    alien = Alien(ai_settings, screen)
    #alien_width = alien.rect.width
    #available_space_x = ai_settings.screen_width - 2 * alien_width
    #number_aliens_x = int(available_space_x / (2 * alien_width))
    number_aliens_x = get_number_aliens_x(ai_settings, alien.rect.width)
    number_rows = get_number_rows(ai_settings, ship.rect.height,
                                  alien.rect.height)

    print('number_rows = '+str(number_rows)+'   ship.rect.height='+str(ship.rect.height)
          +'   alien.rect.height='+str(alien.rect.height))
    #print('alien_width='+str(alien_width))
    #print('\navailable_space_x='+str(available_space_x)+',  number_aliens_x='+str(number_aliens_x))
    #print('\nai_settings.screen_width='+str(ai_settings.screen_width))
    # 创建一群外星人 多行
    for row_number in range(number_rows):
        for alien_number in range(number_aliens_x):
            create_alien(ai_settings, screen, aliens, alien_number, row_number)



def change_fleet_direction(ai_settings, aliens):
    """将整群外星人下移， 并改变它们的方向"""
    for alien in aliens.sprites():
        alien.rect.y += ai_settings.fleet_drop_speed
    ai_settings.fleet_direction *= -1

def ship_hit(ai_settings, stats, screen, ship, aliens, bullets):
    """响应被外星人撞到的飞船"""
    if stats.ships_left > 0:
        # 将ships_left减1
        stats.ships_left -= 1
        # 清空外星人列表和子弹列表
        aliens.empty()
        bullets.empty()
        # 创建一群新的外星人， 并将飞船放到屏幕底端中央
        create_fleet(ai_settings, screen, aliens, ship )
        ship.center_ship()
        # 暂停
        sleep(3)
    else:
        stats.game_active = False

def check_aliens_bottom(ai_settings, stats, screen, ship, aliens, bullets):
    """检查是否有外星人到达了屏幕底端"""
    screen_rect = screen.get_rect()
    for alien in aliens.sprites():
        if alien.rect.bottom >= screen_rect.bottom:
            # 像飞船被撞到一样进行处理
            ship_hit(ai_settings, stats, screen, ship, aliens, bullets)
            break


def update_aliens(ai_settings, stats, screen, ship, aliens, bullets):
    """
    检查是否有外星人位于屏幕边缘， 并更新整群外星人的位置
    """
    check_fleet_edges(ai_settings, aliens)
    aliens.update()
    # 检测外星人和飞船之间的碰撞
    if pygame.sprite.spritecollideany(ship, aliens):
        ship_hit(ai_settings, stats, screen, ship, aliens, bullets)

    # 检查是否有外星人到达屏幕底端
    check_aliens_bottom(ai_settings, stats, screen, ship, aliens, bullets)


def check_fleet_edges(ai_settings, aliens):
    """有外星人到达边缘时采取相应的措施"""
    for alien in aliens.sprites():
        if alien.check_edges():
            change_fleet_direction(ai_settings, aliens)
            break